The goal of this proposal is to elucidate and compare transcriptional events and associated regulatory mechanisms that operate to control expression of the beta-tubulin gene during development (oogenesis and embryogenesis) and during the terminal differentiation process of red blood cell formation (erythropoiesis) in the amphibian, Xenopus laevis. Specifically, I will: (1) clone and selectively analyze a ubiquitous and the erythroid-specific members of the beta-tubulin gene family; (2) study their transcriptional expression during erythroid differentiation and early development; (3) determine the sequence elements that encompass the basic beta-tubulin promotor; (4) initiate an analysis of the proteins involved in formatting the regulation of these genes; (5) localize regions within the erythroid beta-tubulin gene that modulate transcription in a tissue- specific and developmentally appropriate manner. The unique value of this experimental approach is threefold: a) use of erythropoiesis as a model for determining the controls and patterns in expression of differentiation-specific genes; b) use of Xenopus as a well- characterized vertebrate developmental system; c) use of a gene family whose expressed members include both general and tissue-specific isotypes. This will allow cis- and trans-acting transcriptional controls that operate within generally-required isotypes during early development (e.g., expression of ubiquitous beta-tubulin during oogenesis) to be related to those that coordinate expression of distinct isotypes during differentiation (e.g., selective expression of erythroid beta-tubulin). such molecular details of gene regulation within the settings of development and differentiation are of considerable interest, as an multicellular eukaryote faces the same demands of general and selective expression. Lastly, these analyses also will elucidate fundamental aspects of transcriptional regulatory mechanisms operating in a minimally perturbed (ie, non-transformed) system.